Can not access data from given OIDs using net-snmp

Question

i implemented the simple net-snmp simple application into my project. when i tried to use the example OID given at the site: .1.3.6.1.2.1.1.1.0 it worked just fine. now i need to get data from these oids: https://www.sysadmin.md/snmp-most-useful-linux-oids.html. when i tried to implement these oids into my code i got error: Process finished with exit code 139 (interrupted by signal 11: SIGSEGV). the simple application code: add_mibdir(".");

pdu = snmp_pdu_create(SNMP_MSG_GET);//creating a get pdu
if(read_objid(".1.3.6.1.4.1.2021.11.9", id_oid, &id_len)==1)//specifying the oid we want to receive
    cout<<"oid read"<<endl;
else
    cout<<"couldnt read oid"<<endl;
snmp_add_null_var(pdu, id_oid, id_len);//making room for the response
status = snmp_synch_response(session_handle, pdu, &response);//getting the response
cout<<"status: "<<status<<endl;
string ReturnBuffer;
cout<<"vars: "<<vars->val.string<<endl;
for(vars = response->variables; vars; vars = vars->next_variable)//printing the values we got back
{
    cout<<vars->val.string<<endl;
    ReturnBuffer.append(reinterpret_cast<char*>(vars->val.string));
}
ReturnBuffer.append("\0"); //test
return ReturnBuffer;

according to the code the oid itself is read and the status of the response is 0 and yet im not getting any of the data and got the error above, i'd appreciate any help thanks in advance. language: c++ os: linux(ubuntu)